Time effects, Echo effect – Adobe After Effects CS3 User Manual
Page 536
AFTER EFFECTS CS3
User Guide
531
Time effects
Echo effect
The Echo effect combines frames from different times in a layer. The Echo effect has a variety of uses, from a simple
visual echo to streaking and smearing effects. The results of this effect are visible only if there is change across time
in the layer, such as motion.
Note: A layer’s masks and any previously applied effects are ignored by the Echo effect. To echo the frames of a layer with
its masks and effects, precompose the layer before applying the Echo effect.
This effect works with 8-bpc, 16-bpc, and 32-bpc color.
Echo effect
David Van Brink provides a blog post and sample project that show how to use the Echo effect, the Particle
Playground effect, and the loopOut expression to animate a swarm of stylized swimming bacteria:
Echo Time (seconds)
The time, in seconds, between echoes. Negative values create echoes from previous frames;
positive values create echoes from upcoming frames.
Number of Echoes
The number of echoes. For example, if the value is 2, the result is a combination of three frames:
the current time, the current time + Echo Time, and the current time + (2 * Echo Time).
Starting Intensity
The opacity of the first image in the echo sequence.
Decay
The ratio of the opacity of an echo to the opacity of the echo preceding it in the echo sequence. For example,
if Decay is 0.5, then the opacity of the first echo is half of the Starting Intensity; the second echo is half of that, or one
quarter of the Starting Intensity.
Echo Operator
The blending operation used to combine the echoes.
•
Add
Combines the echoes by adding their pixel values. If the starting intensity is too high, this mode can quickly
overload and produce streaks of white.
•
Maximum
Combines the echoes by taking the maximum pixel values from all of the echoes.
•
Minimum
Combines the echoes by taking the minimum pixel values from all of the echoes.
•
Screen
Emulates combining the echoes by sandwiching them optically. This mode is similar to Add, but it won’t
overload as quickly.
•
Composite In Back
Causes the image from the current time to appear in back, with each echo appearing succes-
sively farther forward in the composite.
•
Composite In Front
Causes the image from the current time to appear in front, with each echo appearing succes-
sively farther back in the composite.
•
Blend
Averages the echoes.